To answer this question I can provide a Jewish view – for there is no such thing as the Jewish view. As with Christianity or Islam, there are a wide range of different traditions, ranging from the ultra-conservative to the most liberal, and it is possible to speak passionately from either end of the spectrum with absolute belief in totally opposing conclusions.

Nevertheless, some generalisations can be made. One is that Judaism regards the embryo as containing life in potential, and therefore should be treated with the utmost care and respect. However, Judaism also holds that the embryo does not have the same status as a human that is outside the womb.

This derives from a biblical incident when two men who were fighting injured a pregnant woman standing nearby: if the woman dies, they are liable to the death penalty; if just the foetus dies, then they are merely subject to a fine (Exodus 21:22-23).

This relates directly to the vexed question as to when life begins. For Judaism, life does not begin fully until birth.

This is reinforced by the second most important book in Jewish sacred literature – the Mishnah, compiled around the year 200 – which comments on the case of a pregnant women whose life is endangered by the foetus:

If a woman was in life-threatening labour, the child must be killed while it is in the womb, and brought out, since the life of the mother has priority over the life of the child. But if the greater part of it had already been born, it may not be touched, since the claim of one life cannot override the claim of another life.

(Oholot 7.6)

In this extreme example, it is emergence from the womb that marks the turning point from virtually human to fully human. This likewise is the transition in the accumulation of rights: from being largely protected to being totally protected.

There has been much discussion since then and Judaism certainly takes into account modern insights as to how the embryo develops at different stages and how it can move and feel in the womb. However, the distinction between life in potential and life in actuality remains. Thus within the overall principle of the value of life, a hierarchy of sanctity exists.

This has significant implications for research because it means that terminating a foetus is not murder. It also implies that the regret at the loss involved is outweighed by benefits gained from experimentation which can help humans.

This is not to adopt a cavalier attitude to the foetus – it has to be respected and safeguarded, but in principle there can be certain situations in which its interests can be set aside.

This would equally apply to research on human-animal hybrids. Those who object that it is crossing boundaries are putting emotion in front of reason: a significant number of heart patients are walking around with pig valves inside them, while most humans push bits of animals' bodies down their throat every day! The key question is not "How do I feel about it?" but "will it be a force for good?"

As for the accusation that this involves "playing God" – of course it does! Moreover, Judaism would see this as a compliment, for God has entrusted the world into our care, to better and improve using our God-given abilities. Otherwise we would never develop penicillin, carry out lung transplants or manufacture false limbs.

At the same time there are important considerations as to how we approach such experiments: safeguards have to be put in place so as to prevent abuse, values have to be kept before us so that arrogance does not prevail, and a sense of awe for the sanctity of life has to guide our steps so that we always enhance life and never demean it. That way we become partners with God in the work of creation. We should do so as often as we can, and be licensed accordingly.